As is known in the art, reel-type gaming machines typically include a number of adjacent reels each having a plurality of symbols such as fruit provided on the outer periphery of the reels. The reels are simultaneously caused to start rotation by pulling a handle or pushing a button after inserting a given number of coins or tokens into a coin slot. After the start of rotation, the individual reels are successively brought to a stop after the lapse of random time periods determined by a micro-processor-based control system. When all the reels are stopped, a symbol from each reel is in alignment with a pay line displayed on a window. If the symbols aligned with the pay line are a winning combination, a number of coins corresponding to the probability of occurrence of that combination are paid out from a pay-out slot.
Typically, each reel is provided with an individual stepping motor which drives the reel. Thus, the speed of rotation can be controlled by adjusting the pulse rate and can be kept at a standard value under normal operating conditions. Also, the position of the reel (i.e. the angle of rotation) can be easily controlled in accordance with the total number of pulses supplied to the motor. The control system supplies the pulses to the motor to control the operation and position of the reels.
However, one disadvantage of utilizing stepper motors is unsatisfactory starting and stopping operation. Typically, the inertia of the reel presents a significant load when starting from a standstill or stopping during full rotation, which can result in a jerky and irregular start or stop. There is also a risk that the motor may completely stall, lose positional control, or otherwise operate improperly. The start-up operation can be improved by a reduction in the pulse rate from the standard value over an initial short period. This results in a slow motor output speed at which the motor will start, which then must be accelerated by increasing the pulse rate to the standard value. Even with this ramping up of pulse rate, the startup operation of the motor is somewhat hesitant and causes stress which can lead to undesirable performance of the motor. To avoid this problem, it is desirable to provide a smooth start and stop such as that obtained by the gradual release of a spring when using a purely mechanical drive.
Attempts have been made to provide such a spring action to overcome the inertia of the reel and impart an impulsive start-up movement to the reel. For example, in one such device, an output shaft of the motor is connected to the reel through two O-rings of elastomeric material. The O-rings are fitted on opposing portions of a pin extending transversely through the motor shaft, and engage the sides of an opening in a boss forming part of the reel structure. Thus, the driving torque is transmitted to the reel through the O-rings, which provide a degree of resilience for overcoming the inertia of the reel, thereby providing a quicker, more responsive start to the rotation of the reel. In other words, the resilient O-rings are an attempt to provide a smooth acceleration from the start-up speed to the standard operating speed of the motor.
Although the O-ring type reel mechanisms are a step toward improving start-up operation of the motors, there remains a need for further improvement by providing a more responsive spring action to overcome the inertia of the reel. As will be appreciated, the effect of the O-rings is limited because the spring action can only be imparted to an isolated region in the central hub of the reel. This leads to high stress and increased maintenance costs. It is therefore desirable to provide a mechanism which redistributes the application of the spring force away from the center of the reel structure to facilitate the spring action imparted on the reel.